First lady Michelle Obama today said her global advocacy on behalf of women and young people gives her a personal stake in her husband's re-election, and that she eagerly awaits the coming campaign.

"I think there's so much more work to do. We've really just begun to lay the foundation," Obama told ABC News' David Muir in a wide-ranging interview in Cape Town, South Africa, where she's on a weeklong trip to promote youth leadership, education and political and cultural exchanges.

"I'm passionate about these issues. I want to make sure there's a footing in them in the same way that my husband does," she said. "So, more time would be helpful."

"So you like the job?" Muir asked.

"I love the job, I do. I love people and I like having a positive impact," she said.

Obama, who was an outspoken advocate for her husband during the 2008 campaign, said she enjoys the rigorous schedule of stump speeches, fundraisers, and meetings with supporters across the country.

As for relentless criticism of President Obama and his handling of the job, including from some Democratic corners, the first lady said she follows her husband's lead.

"He's so good at understanding that you just keep building, you don't keep looking back, you don't keep checking polls, you keep doing the work that needs to get done," Obama told Muir. "That's why I like him as my president, because he is really focused on doing what he thinks is the best thing to do even when it's hard."

The Africa trip is Obama's fourth to the continent but first visit to South Africa, where she and her daughters, Sasha and Malia, have captivated national attention in the spotlight.

The Obama family Tuesday visited with former South African president and global anti-apartheid icon Nelson Mandela at his home in Houghton.

"It was powerful because his presence in and of itself was powerful," Obama, 47, said of the experience. "At the same time, it was sort of like being at Thanksgiving dinner because we were surrounded by his family. ... A little chaotic, but a lot of fun, lot of excitement. And there he sat just happy, and that was good to see."

The Chicago native and lawyer said she told Mandela, 92, that his story had a profound impact on her family.

"I said you cannot imagine how important your legacy is to who I am, to who my husband is," she said. "And I just said, thank you, thank you, thank you."

Obama also said the Mandela meeting and outreach to South African children were meaningful experiences for her daughters, who have had to walk a fine line between maintaining privacy and embracing public roles as members of the first family.

Malia, 12, and Sasha, 10, visited a shanty town in Johannesburg Wednesday, when they donated 200 copies of Dr. Seuss's "Cat in the Hat" and took turns reading aloud to children in the crowd.

"I want them to do service to give back and to engage," the first lady told Muir. "They're on the world stage here, but they were also doing something for the kids at that center.

"It's always a balance, but our priority will always be protecting their privacy. It won't be often that you see them reading the "Cat in the Hat," but I think this was an important exception for them."

The first lady also made clear that her motherly instincts extend beyond her immediate family and drive her outreach to young people around the world.

"The thing you realize when you become a mother is that kids don't really even need much, but so many kids aren't getting anything," she said. "These opportunities are my one chance to give hugs and shine that light on a few. ... You have to pass it on, you have to be that little point of light in some child's life so they can find their way to that promise."